Remove CHS information from internal representation of MBR partitions. Generate

CHS information as required when writing MBR to disk, editing a partition in CHS
mode or printing MBR.

No intentional functional change.

5 files changed, 71 insertions, 101 deletions

diff --git a/sbin/fdisk/cmd.c b/sbin/fdisk/cmd.c
index 98aab7a6142..3aca9c75751 100644
--- a/sbin/fdisk/cmd.c
+++ b/sbin/fdisk/cmd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cmd.c,v 1.150 2022/01/27 16:26:32 krw Exp $	*/
+/*	$OpenBSD: cmd.c,v 1.151 2022/02/04 14:07:56 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -190,6 +190,7 @@ parsepn(const char *pnstr)
 int
 edit(const int pn, struct mbr *mbr)
 {
+	struct chs		 start, end;
 	struct prt		*pp;
 	uint64_t		 track;
 	unsigned char		 oldid;
@@ -209,39 +210,34 @@ edit(const int pn, struct mbr *mbr)
 	}
 
 	if (ask_yn("Do you wish to edit in CHS mode?")) {
-		pp->prt_scyl = ask_num("BIOS Starting cylinder", pp->prt_scyl,
+		PRT_lba_to_chs(pp, &start, &end);
+		start.chs_cyl = ask_num("BIOS Starting cylinder", start.chs_cyl,
 		    0, disk.dk_cylinders - 1);
-		pp->prt_shead = ask_num("BIOS Starting head",    pp->prt_shead,
+		start.chs_head = ask_num("BIOS Starting head", start.chs_head,
 		    0, disk.dk_heads - 1);
-		pp->prt_ssect = ask_num("BIOS Starting sector",  pp->prt_ssect,
+		start.chs_sect = ask_num("BIOS Starting sector", start.chs_sect,
 		    1, disk.dk_sectors);
 
-		pp->prt_ecyl = ask_num("BIOS Ending cylinder",   pp->prt_ecyl,
-		    pp->prt_scyl, disk.dk_cylinders - 1);
-		pp->prt_ehead = ask_num("BIOS Ending head",      pp->prt_ehead,
-		    (pp->prt_scyl == pp->prt_ecyl) ? pp->prt_shead : 0,
+		end.chs_cyl = ask_num("BIOS Ending cylinder", end.chs_cyl,
+		    start.chs_cyl, disk.dk_cylinders - 1);
+		end.chs_head = ask_num("BIOS Ending head", end.chs_head,
+		    (start.chs_cyl == end.chs_cyl) ? start.chs_head : 0,
 		    disk.dk_heads - 1);
-		pp->prt_esect = ask_num("BIOS Ending sector",    pp->prt_esect,
-		    (pp->prt_scyl == pp->prt_ecyl && pp->prt_shead ==
-		    pp->prt_ehead) ? pp->prt_ssect : 1, disk.dk_sectors);
+		end.chs_sect = ask_num("BIOS Ending sector", end.chs_sect,
+		    (start.chs_cyl == end.chs_cyl && start.chs_head ==
+		    end.chs_head) ? start.chs_sect : 1, disk.dk_sectors);
 
 		/* The ATA/ATAPI spec says LBA = (C × HPC + H) × SPT + (S − 1) */
-		track = (uint64_t)pp->prt_scyl * disk.dk_heads + pp->prt_shead;
-		pp->prt_bs = track * disk.dk_sectors + (pp->prt_ssect - 1);
-		track = (uint64_t)pp->prt_ecyl * disk.dk_heads + pp->prt_ehead;
-		pp->prt_ns = track * disk.dk_sectors + (pp->prt_esect - 1) -
+		track = start.chs_cyl * disk.dk_heads + start.chs_head;
+		pp->prt_bs = track * disk.dk_sectors + (start.chs_sect - 1);
+		track = end.chs_cyl * disk.dk_heads + end.chs_head;
+		pp->prt_ns = track * disk.dk_sectors + (end.chs_sect - 1) -
 		    pp->prt_bs + 1;
-
-		/* Fix up CHS values for LBA */
-		PRT_fix_CHS(pp);
 	} else {
 		pp->prt_bs = getuint64("Partition offset", pp->prt_bs, 0,
 		    disk.dk_size - 1);
 		pp->prt_ns = getuint64("Partition size",   pp->prt_ns, 1,
 		    disk.dk_size - pp->prt_bs);
-
-		/* Fix up CHS values */
-		PRT_fix_CHS(pp);
 	}
 
 	return 0;
diff --git a/sbin/fdisk/gpt.c b/sbin/fdisk/gpt.c
index d8354810310..fa556c0556f 100644
--- a/sbin/fdisk/gpt.c
+++ b/sbin/fdisk/gpt.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: gpt.c,v 1.56 2022/01/02 17:26:14 krw Exp $	*/
+/*	$OpenBSD: gpt.c,v 1.57 2022/02/04 14:07:56 krw Exp $	*/
 /*
  * Copyright (c) 2015 Markus Muller <mmu@grummel.net>
  * Copyright (c) 2015 Kenneth R Westerback <krw@openbsd.org>
@@ -491,7 +491,6 @@ init_gh(void)
 	gmbr.mbr_prt[0].prt_id = DOSPTYP_EFI;
 	gmbr.mbr_prt[0].prt_bs = 1;
 	gmbr.mbr_prt[0].prt_ns = UINT32_MAX;
-	PRT_fix_CHS(&gmbr.mbr_prt[0]);
 	gmbr.mbr_signature = DOSMBR_SIGNATURE;
 
 	needed = sizeof(gp) / secsize + 2;
diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 90d2def9ea1..1fe0aa0f5ae 100644
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mbr.c,v 1.115 2022/01/21 17:29:24 krw Exp $	*/
+/*	$OpenBSD: mbr.c,v 1.116 2022/02/04 14:07:56 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -91,11 +91,8 @@ MBR_init(struct mbr *mbr)
 		obsdprt.prt_id = DOSPTYP_OPENBSD;
 		if (bootprt.prt_flag != DOSACTIVE)
 			obsdprt.prt_flag = DOSACTIVE;
-		PRT_fix_CHS(&obsdprt);
 	}
 
-	PRT_fix_CHS(&bootprt);
-
 	memset(mbr, 0, sizeof(*mbr));
 	memcpy(mbr->mbr_code, default_dmbr.dmbr_boot, sizeof(mbr->mbr_code));
 	mbr->mbr_prt[0] = bootprt;
diff --git a/sbin/fdisk/part.c b/sbin/fdisk/part.c
index b95a6e76a80..89a5adff13c 100644
--- a/sbin/fdisk/part.c
+++ b/sbin/fdisk/part.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: part.c,v 1.114 2022/02/03 13:24:04 visa Exp $	*/
+/*	$OpenBSD: part.c,v 1.115 2022/02/04 14:07:56 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -30,7 +30,6 @@
 #include "disk.h"
 #include "misc.h"
 
-int			 check_chs(const struct prt *);
 const char		*ascii_id(const int);
 
 struct mbr_type {
@@ -287,52 +286,32 @@ PRT_parse(const struct dos_partition *dp, const uint64_t lba_self,
 	prt->prt_ns = letoh32(t);
 	if (prt->prt_id == DOSPTYP_EFI && prt->prt_ns == UINT32_MAX)
 		prt->prt_ns = DL_GETDSIZE(&dl) - prt->prt_bs;
-
-	PRT_fix_CHS(prt);
-}
-
-int
-check_chs(const struct prt *prt)
-{
-	if ( (prt->prt_shead > 255) ||
-		(prt->prt_ssect >63) ||
-		(prt->prt_scyl > 1023) ||
-		(prt->prt_ehead >255) ||
-		(prt->prt_esect >63) ||
-		(prt->prt_ecyl > 1023) )
-	{
-		return -1;
-	}
-	return 0;
 }
 
 void
 PRT_make(const struct prt *prt, const uint64_t lba_self, const uint64_t lba_firstembr,
     struct dos_partition *dp)
 {
+	struct chs		start, end;
 	uint64_t		off, t;
-	uint32_t		ecyl, scyl;
 
 	if (prt->prt_ns == 0 || prt->prt_id == DOSPTYP_UNUSED) {
 		memset(dp, 0, sizeof(*dp));
 		return;
 	}
 
-	scyl = (prt->prt_scyl > 1023) ? 1023 : prt->prt_scyl;
-	ecyl = (prt->prt_ecyl > 1023) ? 1023 : prt->prt_ecyl;
-
 	if ((prt->prt_id == DOSPTYP_EXTEND) || (prt->prt_id == DOSPTYP_EXTENDL))
 		off = lba_firstembr;
 	else
 		off = lba_self;
 
-	if (check_chs(prt) == 0) {
-		dp->dp_shd = prt->prt_shead & 0xFF;
-		dp->dp_ssect = (prt->prt_ssect & 0x3F) | ((scyl & 0x300) >> 2);
-		dp->dp_scyl = scyl & 0xFF;
-		dp->dp_ehd = prt->prt_ehead & 0xFF;
-		dp->dp_esect = (prt->prt_esect & 0x3F) | ((ecyl & 0x300) >> 2);
-		dp->dp_ecyl = ecyl & 0xFF;
+	if (PRT_lba_to_chs(prt, &start, &end) == 0) {
+		dp->dp_shd = start.chs_head & 0xFF;
+		dp->dp_ssect = (start.chs_sect & 0x3F) | ((start.chs_cyl & 0x300) >> 2);
+		dp->dp_scyl = start.chs_cyl & 0xFF;
+		dp->dp_ehd = end.chs_head & 0xFF;
+		dp->dp_esect = (end.chs_sect & 0x3F) | ((end.chs_cyl & 0x300) >> 2);
+		dp->dp_ecyl = end.chs_cyl & 0xFF;
 	} else {
 		memset(dp, 0xFF, sizeof(*dp));
 	}
@@ -365,57 +344,54 @@ void
 PRT_print_part(const int num, const struct prt *prt, const char *units)
 {
 	const struct unit_type	*ut;
+	struct chs		 start, end;
 	double			 size;
 
 	size = units_size(units, prt->prt_ns, &ut);
-	printf("%c%1d: %.2X %6u %3u %3u - %6u %3u %3u "
+	PRT_lba_to_chs(prt, &start, &end);
+
+	printf("%c%1d: %.2X %6llu %3u %3u - %6llu %3u %3u "
 	    "[%12llu:%12.0f%s] %s\n",
 	    (prt->prt_flag == DOSACTIVE)?'*':' ',
 	    num, prt->prt_id,
-	    prt->prt_scyl, prt->prt_shead, prt->prt_ssect,
-	    prt->prt_ecyl, prt->prt_ehead, prt->prt_esect,
+	    start.chs_cyl, start.chs_head, start.chs_sect,
+	    end.chs_cyl, end.chs_head, end.chs_sect,
 	    prt->prt_bs, size, ut->ut_abbr, ascii_id(prt->prt_id));
 }
 
-void
-PRT_fix_CHS(struct prt *prt)
+int
+PRT_lba_to_chs(const struct prt *prt, struct chs *start, struct chs *end)
 {
-	uint32_t		spt, tpc, spc;
-	uint32_t		start, end, size;
-	uint32_t		cyl, head, sect;
+	uint64_t		lba;
 
-	if (prt->prt_id == DOSPTYP_UNUSED || prt->prt_ns == 0) {
-		memset(prt, 0, sizeof(*prt));
-		return;
+	if (prt->prt_ns == 0 || prt->prt_id == DOSPTYP_UNUSED) {
+		memset(start, 0, sizeof(*start));
+		memset(end, 0, sizeof(*end));
+		return -1;
 	}
 
-	spt = disk.dk_sectors;
-	tpc = disk.dk_heads;
-	spc = spt * tpc;
-
-	start = prt->prt_bs;
-	size = prt->prt_ns;
-	end = (start + size) - 1;
-
-	cyl = (start / spc);
-	start -= (cyl * spc);
-	head = (start / spt);
-	start -= (head * spt);
-	sect = (start + 1);
-
-	prt->prt_scyl = cyl;
-	prt->prt_shead = head;
-	prt->prt_ssect = sect;
-
-	cyl = (end / spc);
-	end -= (cyl * spc);
-	head = (end / spt);
-	end -= (head * spt);
-	sect = (end + 1);
-
-	prt->prt_ecyl = cyl;
-	prt->prt_ehead = head;
-	prt->prt_esect = sect;
+	/*
+	 * C = LBA ÷ (HPC × SPT)
+	 * H = (LBA ÷ SPT) mod HPC
+	 * S = (LBA mod SPT) + 1
+	 */
+
+	lba = prt->prt_bs;
+	start->chs_cyl = lba / (disk.dk_sectors * disk.dk_heads);
+	start->chs_head = (lba / disk.dk_sectors) % disk.dk_heads;
+	start->chs_sect = (lba % disk.dk_sectors) + 1;
+
+	lba = prt->prt_bs + prt->prt_ns - 1;
+	end->chs_cyl = lba / (disk.dk_sectors * disk.dk_heads);
+	end->chs_head = (lba / disk.dk_sectors) % disk.dk_heads;
+	end->chs_sect = (lba % disk.dk_sectors) + 1;
+
+	if (start->chs_head > 255 || end->chs_head > 255 ||
+	    start->chs_sect > 63  || end->chs_sect > 63 ||
+	    start->chs_cyl > 1023 || end->chs_cyl > 1023)
+		return -1;
+
+	return 0;
 }
 
 char *
diff --git a/sbin/fdisk/part.h b/sbin/fdisk/part.h
index e7db6c08abf..7b20ac5c7f9 100644
--- a/sbin/fdisk/part.h
+++ b/sbin/fdisk/part.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: part.h,v 1.33 2022/01/27 16:26:32 krw Exp $	*/
+/*	$OpenBSD: part.h,v 1.34 2022/02/04 14:07:56 krw Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -16,11 +16,15 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+struct chs {
+	uint64_t	chs_cyl;
+	uint32_t	chs_head;
+	uint32_t	chs_sect;
+};
+
 struct prt {
 	uint64_t	prt_bs;
 	uint64_t	prt_ns;
-	uint32_t	prt_shead, prt_scyl, prt_ssect;
-	uint32_t	prt_ehead, prt_ecyl, prt_esect;
 	unsigned char	prt_flag;
 	unsigned char	prt_id;
 };
@@ -37,6 +41,4 @@ char		*PRT_uuid_to_typename(const struct uuid *);
 int		 PRT_uuid_to_type(const struct uuid *);
 struct uuid	*PRT_type_to_uuid(const int);
 int		 PRT_protected_guid(const struct uuid *);
-
-/* This does bs/ns -> CHS */
-void PRT_fix_CHS(struct prt *);
+int		 PRT_lba_to_chs(const struct prt*, struct chs *, struct chs*);